I like your translation of this line as it is very literal:
"Let each be most observed who meets the eyes of her unexpected husband on his arrival."
In my opinion the best version (even if it's not the most literal) is Reverend Canon Roberts' 1912 translation:
What we see of the behaviour, of each on the unexpected arrival of her husband, let that be the surest test.’
If I could paraphrase, I think he's saying:
When the husband arrives unexpectedly and their eyes meet, let's carefully observe the behavior of each one.